The present invention related generally to a method and apparatus for forming a multi-layer structure for the assembly into a capacitor, for example. Multi-layer structures are particularly known in electrical components in order, generally, to increase the power of electrical single-layer components by providing multiple arrangements above one another.
U.S. Pat. No. 5,621,607 discloses capacitors with a multi-layer structure that, for example, are composed of a plurality of electrode layers between which a dielectric is respectively arranged. The capacitor with multi-layer structure thereby comprises a multiple of the capacitance that attaches to an individual capacitor element composed of two electrode layers with dielectric arranged therebetween. What applies as a rule of thumb is that the power or, respectively, the capacitance of the capacitor with multi-layer structure derives from the product of the capacitance of a single capacitor element and the plurality of capacitor elements.
DE 198 04 584 C2 discloses a double layer capacitor having at least two series-connected, individual cells. It comprises an alternating arrangement of electrode layers and the electrolyte layers and is manufactured by stacking up and pressing the individual layers. JP 11-260673 A discloses a double layer capacitor for whose-manufacture positive and negative electrodes are embedded in alternation in a band-shaped separator that is subsequently folded meander-like, so that a stack with alternating arrangement of positive and negative electrodes is obtained.
Another advantage of a multi-layer structure is comprised therein that the field strength between two electrode layers increases with decreasing electrode spacing. This enhanced field strength is also of interest for other components, for example for a piczo-actuator in multi-layer structure wherein the individual piezo-actuator elements are arranged above one another. Such a piezo-actuator having multi-layer structure can be operated with a far lower operating voltage then a correspondingly single-layer piezo-actuator having the same layer thickness of piezo-material or, respectively, having the same maximum piezo-electrically induced excursion.
Dependent on the function and application, components have a multi-layer structure can be implemented or, respectively, manufactured as a more or less loose stacking of individual layers above one another. Particularly given mechanical stressing, however, a firmer union of the individual layers is required in the multi-layer structure in order to lend the whole an adequate mechanical stability. A monolithic union is desired for components having ceramic multi-structure.
Given multi-layer capacitors, particularly with liquid electrolyte, the electrode layers are arranged in alternation above one another with intermediate layers that are not electrically conductive. In particular, a separator folder meander-like is thereby employed for the intermediate layer, the electrode layers being inserted into the xe2x80x9cpocketsxe2x80x9d thereof. The electrode layers can there by also comprise a multi-layer structure; in said multi-layer capacitor, for example, they can comprise a three-layer structure composed of two porous carbon layers with intervening, metallic electrode layer, for example of aluminum. For manufacture, the different electrode layers are individually stacked on top of one another. A separate work step is thereby required for each layer or, respectively, each ply. When stacking such individual elements or, respectively, individual layers, problems then arise regarding the exact positioning of the layers, these, on the one hand, deteriorating the reproducibility and, on the other hand, leading to faulty components or components with reduced power. Particularly given layers that become thinner and thinner, the manipulation of the individual layers is also made more difficult since these layers are becoming increasingly more flexible and less mechanical stable at the same time.
It is therefore an object of the present invention to specify a method for manufacturing regular multi-layer structures suitable for, in particular, components that is simplified with respect to the implementation and dependably and exactly leads to the desired result.
This object is achieved with a method according to claim 1. Advantageous developments of the method as well as an apparatus for the manufacture of a multi-layer structure can be derived from the further claims.
The present invention is based on the basic idea of designing the manufacture of multi-layered structures as a continuous process since the repeating layer sequences in the multi-layer structure also produce repeating method steps. The most mechanically stable layer forms the base, this serving as a carrier material and being present in a band-shaped material, particularly as an xe2x80x9cendless bandxe2x80x9d.
The parting of the band-shaped carrier material into individual sections having the desired size and shape thereby ensues in at least two steps. In a first, partial separation step, the carrier material is divided into the individual carrier sections, whereby a connection that is capable of bearing remains between two respective individual, neighboring sections, the connection being fashioned, for example, web-like. As a result thereof, the continuous further processing of the carrier material at the section is possible. In the next step, the continuous application of at least one further material layer on one of the surfaces of the band-shaped carrier material ensues. Only after this step are the individual sections having the desired size separated completely from one another along a predetermined parting line, whereby the parting line lies above the partial separation that has already ensued.
The identical multi-layer sections that are thereby obtained are now joined to form the multi-layer structure by being regularly stacked on top of one another. As warranted, an intervening layer that can likewise comprise a multi-layer structure can thereby be respectively inserted between two multi-layer sections.
The method has the advantage that it can be continuously implemented, and that the smallest sections to be processed are already multi-layer sections that need not be individually stacked on top of one another. The multi-layer sections have the advantage that, due to the integrated process management, they comprise a uniform and exact structure. The problem of exact positioning has thus been solved within an individual multi-layer section. Deriving as a further advantage of the parting ensuing in two steps is that the basic areas of the individual layers, i.e. the basic area of the carrier sections and of the at least one further material layer, can be differently selected. It is thus possible to embed one material layer, particularly the carrier material, nearly completely between the other material layers. The cut edge of the carrier material then remains visible from the outside in the finished component only in the region of the most recently parted webs. This is advantageous particularly given metallic carrier materials that can form sharp cut edges, these in turn potentially representing a disturbing factor in the further-processing or in the manipulation of the component.
It is also possible with the method to apply not only one material layer on the carrier substrate but to apply further layers on the same surface or on the opposite surface simultaneously or following thereupon. It is also possible to set a different size of the sections by means of further, additional cuts for each individual material layer in order, in particular, to nearly completely embed internally disposed layers in the multi-layer section without a cut edge being visible from the outside. Only that part of the edge of the carrier material or of some other inwardly disposed layer that is parted in the last parting step as part of the bearing connection is then still visible.
Particularly given multi-layer sections having more then three individual layers, it is also possible to implement the parting in three steps, whereby the bearing connection remaining in the first partial separation is parted in a second partial separation after application of a further material layer, whereby, however, a part of the second material layer should remain as a remaining connection between two neighboring sections. In this case, the three parting lines can be placed such that a cut edge of the carrier material layer is no longer visible from the outside in the multi-layer section.
Different section sizes in the individual material layers can only be achieved when the partial separation in individual sections does not exclusively follow the parting line between two neighboring sections. On the contrary, it is necessary in this case that a broad parting line be placed in the partial separation between two respective neighboring sections orxe2x80x94betterxe2x80x94that a parting strip to be punched out or removed in some other way. When the subsequent, further partial separation or the complete parting into individual multi-layer sections subsequently ensues with a smaller cutting width or even as a sharp separation along a parting line, then the area difference of the individual sections can maximally correspond to the area of a parting strip.
In an advantageous development of the invention, it is already achieved in two-layer multi-layer sections that the externally visible cut edge of a material layer is displaced inwardly with a smaller section area compared to other layers and is thus less disturbing. This is achieved when the parting line in the complete separation forms a recess pointing toward the middle of the section in the region of the bearing connection. In order for this to be the case given two neighboring sections, the web for this purpose is preferably parted by punching, for example a circular cutout.
This is of interest particularly for the multi-layer structure, whereby the cut edge is then situated in a recess that is set back retreats from the limiting surface of the multi-layer structure.